A variety of automatic disc loading and unloading systems have thus far been proposed and put to use for audio and/or video disc playback apparatus. One of the drawbacks which have been inherent in such prior-art automatic disc loading and unloading systems is the objectionably large-sized construction of the system required for the accommodation of the movements of the recording disc to be loaded into and thereafter unloaded out of the playback apparatus.
In a prior-art automatic disc loading and unloading system, furthermore, a disc carrier mechanism is used in which the recording disc being loaded into or unloaded out of the playback apparatus is seized between a pair of disc retaining members which are held in pressing engagement with the outer circumferential edge of the disc and which is forced to press the disc in radial directions of the disc. If the retaining members of the disc carrier mechanism of this nature are pressed against the circumferential edge of the disc by means of preloaded springs, the pressing forces exerted on the recording disc from such spring-loaded retaining members may happen to be excessive unless the spring constants of the springs urging the retaining members against the circumferential edge of the disc are properly selected to be compatible with recording discs of any sizes and/or if the springs, spring-loaded retaining members and any other members and elements associated with the springs and spring-loaded retaining members are not correctly and precisely sized, designed and/or arranged. If excessive pressing forces are applied radially to the circumferential edge of the recording disc being carried by and between the spring-loaded retaining members, the recording disc might be forced to warp or otherwise deformed by such forces.
Another drawback which has been inherent in a prior-art automatic disc loading and unloading system of a recording disc playback apparatus is the disproportionately intricate construction of the mechanism by means of which the recording disc loaded into the playback apparatus is to be brought into a correct position having its center axis aligned with the axis of rotation of the turntable of the playback apparatus.
When, furthermore, a recording disc is to be withdrawn from a playback apparatus upon completion of the playback operation with the disc, the recording disc released from the turntable of the playback apparatus is conveyed to withdraw from the playback apparatus under the guidance of a disc guide panel which projects from the front end of the casing structure of the apparatus so as to prevent the disc from falling from the casing structure while the disc is being withdrawn from the playback apparatus. The provision of such a disc guide panel requires an objectionally large space in front of the casing structure of the playback apparatus and, thus, not only impairs the external appearance of the playback apparatus as a whole but the presence of the guide panel underneath the disc withdrawn from the casing structure tends to hinder the disc from being manually removed from the playback apparatus.
The guide structure or mechanism used for guiding the passage of a recording disc into and out of the casing structure of an audio and/or video disc playback apparatus using a conventional automatic disc loading and unloading system is usually fixedly connected to or integral with the casing structure, particularly the front wall portion or panel member of the casing structure. Furthermore, the various operational units and assemblies such as, for example, the turntable assembly, turntable drive unit, pickup arm assembly, pickup-arm drive assembly and so forth of the playback apparatus are mounted on a support structure which is also usually secured to or integral with the casing structure of the playback apparatus. The casing structure of a playback apparatus is usually arranged to have a component unit or some coponent units such as an amplifier unit mounted thereon when the playback apparatus is installed for use. During operation of the disc playback apparatus thus arranged, the shocks and vibrations which may be produced by the motions and movements of these operational units and assemblies mounted on such a support structure are therefore transferred through the casing structure to the component unit or units through the casing structure. Such a problem could be solved if the support structure is positioned within the casing structure by means of shock absorbing support elements.
On the other hand, an audio and/or video disc playback apparatus of the type equipped with an automatic disc loading and unloading system is usually provided with a disc-size responsive automatic pickup-arm lead-in control device which is adapted to detect the size, or diameter, of the recording disc to be played back and to enable the pickup arm of the playback apparatus to control the automatic drive means for the pickup arm to drive the pickup arm for lead-in motion from the rest position thereof automatically to a position which is predetermined for the size of the recording disc to be played back. In a prior-art automatic disc loading and unloading system of a playback apparatus of this type, such a pick-up-art lead-in control device ordinarily uses contactless size detection means utilizing, for example, photoelectric transducer elements adapted to produce an electric signal representative of the particular size, or diameter, of the recording disc to be played back. The electric signal thus produced by the photoelectric transducer elements is supplied to a control circuit and is converted into a suitable control signal to dictate the motion of the automatic pickup arm drive means. One of the problems encountered in an automatic disc loading and unloading system using a pickup-arm lead-in control device of this nature is the high production cost resulting from the use of the costly photoelectric transducer elements as the contactless size detection means and further from the provision of an electro-mechanical conversion unit which is required for the conversion of an electric control signal into a corresponding mechanical displacement in the automatic pickup arm drive means. Another problem results from the necessity of providing an extra control circuit for precluding the size detection means from being erroneously responsive to the size of the recording disc conveyed to an incorrect position with respect to the turntable of the playback apparatus.
In order that the recording disc to be played back be enabled to be correctly positioned on the turntable of a playback apparatus, there has been proposed a disc support assembly which is adapted to cause the turntable to move upwardly until the spindle projecting from the turntable is inserted upwardly through the center hole in the recording disc which has been conveyed into a correct position above and with respect to the turntable. Problems have been experienced in a disc support assembly of this nature in that the disc support assembly per se is excessively intricate in construction and accordingly excessively expensive; and in that extreme precision machining is required for the fabrication of the turntable and the turntable lifting mechanism supporting the turntable rotatably with respect to the lifting mechanism by means of precision bearings.
These problems are encountered in connection with recording discs of the non-donut-shaped types but similar problems are experienced in connection with recording discs of the donut-shaped types such as extended play (EP) discs. For the playback of an extended play disc, the disc is placed and held in coaxial position on the turntable of the playback apparatus by means of a special adapter, herein referred to as EP adapter in lieu of the spindle for recording discs of the non-donut-shaped types. In an automatic disc loading and unloading system of a playback apparatus, a disc support assembly including such an EP adapter is designed in such a manner as to be capable of projecting upwardly from the center hole in the donut-shaped or extended play disc or being withdrawn into the upwardly open concavity in the turntable when the EP adapter is depressed downwardly or caused to turn about the center axis of the recording disc placed on the turntable. Not only is such a disc support assembly extremely intricate in construction and arrangement but, prior to the loading of a recording disc into the playback apparatus, cumbersome manipulation of the EP adapter depending upon the size of the disc is necessitated for the user of the playback apparatus.
On the other hand, an automatic disc loading and unloading system of a disc playback apparatus usually comprises a disc inlet and outlet opening at the front of the casing structure of the playback apparatus and a disc transfer mechanism adapted to convey the disc into or out of the casing structure through such an opening prior to or upon completion, respectively, of the playback operation with the recording disc. In a disc loading and unloading system of this nature, a disc advance detection device is provided intermediate between the disc inlet and outlet opening and the disc transfer mechanism of the system so as to detect the advancing movement of the recording disc manually inserted into the casing structure through the disc inlet and outlet opening. A problem is pointed out in connection with an automatic disc loading and unloading system of this nature in that the recording disc inserted into the casing structure by manual effort must be further pressed into the casing structure by human intervention after the disc transfer mechanism has been actuated and made ready to drive the recording disc to travel inwardly of the casing structure. Another problem encountered in the automatic disc, loading and unloading system is that the disc transfer mechanism is left in a driven condition if the recording disc, once inserted manually into the casing structure and brought into the position to actuate the detection device fails to be further pressed to move deeper into the casing structure by manual effort.
The disc transfer mechanism of a prior-art automatic disc loading and unloading system of a playback apparatus is adapted solely to drive a recording disc toward and away from the turntable of the playback apparatus, but is not capable of lending itself to correctly positioning the disc with respect to the turntable. If, therefore, the recording disc which has been conveyed into a position above the turntable by means of such a disc transfer mechanism, fails to be correctly positioned with respect to the turntable, the recording disc in such an incorrect position would be raised by the spindle when the turntable is lifted to cause the spindle to pass through the center hole in the disc and, as a consequence, would not be correctly received on the upper face of the turntable with the spindle inserted through the center hole in the disc. Such an inconvenience could be avoided if the disc transfer mechanism per se is capable of not only driving the recording disc toward and away from the turntable but correctly and accurately adjusting the direction of advance of the recording disc being conveyed toward the turntable.
Furthermore, one of the important requirements of an audio and/or video disc playback apparatus of the type equipped with an automatic disc loading and unloading system is to eliminate the possibility of double loading of recording discs for preventing a recording disc from being loaded into the playback apparatus during playback operation of another recording disc. An automatic disc loading and unloading apparatus of a playback apparatus is therefore provided with double loading preventive means adapted to avoid such double loading of a recording disc into the playback apparatus. The double loading preventive means of a conventional automatic disc loading and unloading apparatus has been composed of blocking members arranged to move into and out of the path of a recording disc toward the turntable of the playback apparatus and extra drive means adapted to drive the blocking members for movement through the path. The provision of such blocking members and drive means adds to the complexity of the entire construction and arrangement of the automatic disc loading and unloading system of the playback apparatus. The construction and arrangement of the automatic disc loading and unloading system of a playback apparatus could however be significantly simplified if these extra members and means are elimited from the system.
The double loading preventive means of a prior-art automatic disc loading and unloading system of a playback apparatus has had another drawback in that the blocking members of such means must be actuated at timings controlled with utmost accuracy.
On the other hand, audio and/or video recording discs are presently available in three standardized sizes and are thus categorized in size into small-sized or 7-inch diameter recording discs, medium-sized or 10-inch diameter recording discs, and large-sized or 12-inch diameter recording discs. The recording disc loaded into a playback apparatus for reproducing purposes must for this reason be correctly positioned with respect to the turntable of the playback apparatus depending upon the size or diameter of the particular recording disc. An automatic disc loading and unloading system of a playback apparatus has usually incorporated therein a selective disc positioning mechanism which is responsive to the size or diameter of the disc loaded into the playback apparatus and which is capable of automatically guiding the recording disc into a correct coaxial position with respect to the turntable depending upon the detected size or diameter of the disc. The selective disc positioning mechanism of a prior-art automatic disc loading and unloading system of a playback apparatus has, however, been so complex in construction and arrangement and accordingly so expensive in production cost that from an economical point of view, such a mechanism has not had fully acceptable simplicity of construction.
The selective disc positioning mechanism of an automatic disc loading and unloading system of a playback apparatus is, furthermore, required to resume its initial condition upon withdrawal of a recording disc of any size from the playback apparatus after each playback operation so that the positioning mechanism is capable of being ready to be responsive to the size of the recording disc to be put into subsequent playback operation. An automatic disc loading and unloading system including a selective disc positioning mechanism is therefore further provided with reset means operative to place the positioning mechanism into the initial condition thereof in response to the termination of a playback operation with a recording disc. The reset means for the selective disc positioning mechanism of a conventional automatic disc loading and unloading system of a playback apparatus has however been constructed and arranged to operate various component units of the positioning mechanism individually of one another and has, for this reason, not only been complex in construction and arrangement and accordingly expensive in production cost but required intricate controls for enabling the component units of the mechanism to be operated accurately and with certainty.
The reset means of the automatic disc loading and unloading system of a playback apparatus is actuated by suitable departure detection means responsive to the withdrawal of a recording disc from the playback apparatus upon completion of the playback operation with the recording disc. Such departure detection means of a prior-art automatic disc loading and unloading system of a playback apparatus has been of the type using contactless departure responsive elements such as photoelectric transducer elements and has therefore been disproportionately expensive due to the high prices of the photoelectric transducer elements.
The present invention contemplates provision of an audio and/or video disc playback apparatus featuring an improved automatic disc loading and unloading system which is adapted to solve and eliminate the above described problems and drawbacks which have thus far been inherent and/or encountered in prior-art automatic disc loading and unloading systems of audio and/or video disc playback apparatus.